(1) Field of the Invention
The present invention relates to a magnetic field probe which provides detection of a magnetic field from a device under test in the vicinity of the probe. Further, the present invention relates to a magnetic field measuring system having at least one magnetic field probe in which a magnetic field measurement is performed by detection of a magnetic field from a device under test in the vicinity of the probe.
The present invention is applied to magnetic field measurement to measure electromagnetic noise or electric current as an unwanted electromagnetic signal produced by electrical devices, electronic devices and printed circuit boards provided therein. Such a noise may degrade the performance of the electrical/electronic devices. The results of the magnetic field measurement are used to take preventive measures to reduce the electromagnetic noise from the electrical/electronic devices and the printed circuit boards therein, so as to be in compliance with legal electromagnetic compatibility (EMC) controls or electromagnetic interference prevention.
(2) Description of the Related Art
Legal electromagnetic compatibility (EMC) controls are provided in order to take preventive measures for electrical devices, electronic devices and printed circuit boards provided therein to reduce electromagnetic noise produced by the electrical/electronic devices and the printed circuit boards to a level below the specified level of the legal EMC controls. In order to take preventive measures for the electrical/electronic devices and the printed circuit boards, the legal EMC controls provide some procedures of magnetic field measurement to measure electromagnetic noise or electric current as the source of electromagnetic noise produced by a device under test (DUT).
As one of the above-mentioned procedures of magnetic field measurement, an electromagnetic field at a remote location (for example, at a distance of 10 or 30 meters) of a device under test (DUT) in an open site or within a radio-frequency anechoic chamber as specified by the legal EMC controls is measured by using a specified antenna. The result of the measurement by this procedure is used to take preventive measures for the electrical/electronic devices and the printed circuit boards in order to be in compliance with the legal EMC controls.
There is another procedure of magnetic field measurement. In this procedure, a magnetic field of the device under test (DUT) in the vicinity of a magnetic field probe is detected, and a magnetic field measurement is carried out by detection of the magnetic field from the DUT. This procedure is performed prior to performing the measurement in the open site or within the radio-frequency anechoic chamber. The result of the magnetic field measurement by this procedure is used to take preventive measures for the electrical/electronic devices and the printed circuit boards in order to be in compliance with the legal EMC controls. A description of the related art of the present invention will be given below.
Japanese Laid-Open Patent Application No. 58-048877 discloses a search coil which detects a magnetic field from a device under test, and a method of production of the search coil. In the search coil of the above-mentioned publication, a coil having a concentric arrangement is provided on a flexible substrate which is 0.1-0.3 mm thick, and stranded cables are connected to the ends of the coil. In the production method for the search coil, a metallic foil of copper which is 0.03-0.06 mm thick is attached to the flexible substrate, and a photo-lithographic process is performed so that a coil having a concentric arrangement is formed on the substrate by the metallic foil. The stranded cables are connected to wires from the ends of the coil.
In the search coil of the above-mentioned publication, a wire connection must be provided between the ends of the coil and the stranded cables. In a case in which a small coil having a size below 1 mm is provided in a magnetic field probe, a magnetic field from the device under test may distort in the wire connection in the search coil. The distortion of magnetic field may produce a significant error in the magnetic field detection, and the search coil of the above publication fails to provide adequate accuracy of a magnetic field measurement.
Japanese Laid-Open Patent Application No. 62-106379 discloses a magnetic field measuring probe which detects a magnetic field from a device under test. In the probe of the above-mentioned publication, two looped coils having a symmetric arrangement, and microstrip transmission lines which receive signals from the coils are provided. The transmission lines extend from the coils via lead wires. The coils are not shielded, and the transmission lines are shielded by a shield case.
In the magnetic field measuring probe of the above-mentioned publication, a wire connection must be provided between the coils and the transmission lines. In a case in which a small coil having a size below 1 mm is provided in a magnetic field probe, a magnetic field from the device under test may distort in the wire connection in the probe. The distortion of magnetic field may produce a significant error in the magnetic field detection, and the probe of the above publication fails to provide adequate accuracy of a magnetic field measurement. In addition, in the magnetic field measuring probe of the above publication, the probe including the coils and the transmission lines are packaged on a substrate of a printed circuit board. It is difficult to provide a small coil having a size below 1 mm in the probe.
Japanese Laid-Open Patent Application No. 7-191058 discloses a microwave frequency testing device. In the testing device of the above-mentioned publication, a sensor is provided on a microwave transmission line on a flexible substrate, the sensor being formed by etching. A lead wire extends from the sensor in an elbow-like manner, and an output connector at the leading edge of the lead wire is connected to the sensor through the lead wire.
In the testing device of the above-mentioned publication, a wire connection must be provided between the sensor and the output connector. In a case in which a small coil having a size below 1 mm is provided in a magnetic field probe, a magnetic field from the device under test may distort in the wire connection in the testing device. The distortion of the magnetic field may produce a significant error in the magnetic field detection, and the testing device of the above publication fails to provide adequate accuracy of a magnetic field measurement.
An object of the present invention is to provide an improved magnetic field probe in which the above-described problems are eliminated.
Another object of the present invention is to provide a magnetic field probe which efficiently prevents the distortion of a magnetic field at the lead wires between a coil and pads within the probe, and provides adequate accuracy of a magnetic field measurement for a device under test in the vicinity of the probe.
Still another object of the present invention is to provide a magnetic field measuring system having at least one probe which efficiently prevents the distortion of the magnetic field at the lead wires between a coils and pads within the pad, so that the measuring system provides adequate accuracy of a magnetic field measurement for a device under test in the vicinity of the probe.
The above-mentioned objects of the present invention are achieved by a magnetic field probe comprising: a substrate; a conductive layer, provided on the substrate, which has a coil, lead wires, and pads, the coil having one or a plurality of turns and outputting a signal indicative of a magnetic field from a device under test in the vicinity of the magnetic field probe, the lead wires extending from the coil to the pads, the signal from the coil being transmitted to the pads through the lead wires; an isolating layer of a dielectric material which is provided on the lead wires to protect the lead wires between the coil and the pads in the conductive layer; and a shielding layer of a conductive material which is provided on the isolating layer to protect the isolating layer, wherein the shielding layer prevents distortion of the magnetic field at the lead wires in conjunction with the isolating layer.
The above-mentioned objects of the present invention are achieved by a magnetic field measuring system comprising: at least one probe; and a probe supporting member which supports the at least one probe thereon, the at least one probe comprising: a substrate; a conductive layer, provided on the substrate, which has a coil, lead wires, and pads, the coil having one or a plurality of turns and outputting a signal indicative of a magnetic field from a device under test in the vicinity of the magnetic field probe, the lead wires extending from the coil to the pads, the signal from the coil being transmitted to the pads through the lead wires; an isolating layer of a dielectric material which is provided on the lead wires to protect the lead wires between the coil and the pads in the conductive layer; and a shielding layer of a conductive material which is provided on the isolating layer to protect the isolating layer, wherein the shielding layer prevents distortion of the magnetic field at the lead wires in conjunction with the isolating layer.
The above-mentioned objects of the present invention are achieved by a magnetic field probe comprising: a substrate; a first conductive layer which is provided on the substrate to partially cover the substrate, the first conductive layer having an external peripheral portion; a first isolating layer which is provided on the first conductive layer to overlap with the first conductive layer; a second conductive layer which is provided on the first isolating layer, the second conductive layer having a coil, an internal conductor, and a first pad, the coil having a first end connected to the external peripheral portion of the first conductor layer and having a second end connected to the internal conductor, the coil outputting a signal indicative of a magnetic field from a device under test in the vicinity of the probe, the internal conductor extending from the coil to the first pad, the signal from the coil being transmitted to the first pad through the internal conductor; a second isolating layer which is provided on both the first isolating layer and the second conductive layer to overlap with the first isolating layer so that the internal conductor in the second conductive layer is protected by the second isolating layer; and a third conductive layer which is provided on the second isolating layer, the third conductive layer being connected to the first conductive layer at positions on both sides of the internal conductor so that the first and the third conductive layers form a shielding layer to protect the internal conductor in the second conductive layer, the shielding layer preventing distortion of the magnetic field at the internal conductor in conjunction with the second isolating layer, wherein a second pad is provided in the third conductive layer, the second pad being connected to the first end of the coil through the external peripheral portion of the first conductive layer.
The above-mentioned objects of the present invention are achieved by a magnetic field measuring system comprising: at least one probe; and a probe supporting member for supporting the at least one probe thereon, the at least one probe comprising: a substrate; a first conductive layer which is provided on the substrate to partially cover the substrate, the first conductive layer having an external peripheral portion; a first isolating layer which is provided on the first conductive layer to overlap with the first conductive layer; a second conductive layer which is provided on the first isolating layer, the second conductive layer having a coil, an internal conductor, and a first pad, the coil having a first end connected to the external peripheral portion of the first conductor layer and having a second end connected to the internal conductor, the coil outputting a signal indicative of a magnetic field from a device under test in the vicinity of the probe, the internal conductor extending from the coil to the first pad, the signal from the coil being transmitted to the first pad through the internal conductor; a second isolating layer which is provided on both the first isolating layer and the second conductive layer to overlap with the first isolating layer so that the internal conductor in the second conductive layer is protected by the second isolating layer; and a third conductive layer which is provided on the second isolating layer, the third conductive layer being connected to the first conductive layer at positions on both sides of the internal conductor so that the first and the third conductive layers form a shielding layer to protect the internal conductor in the second conductive layer, the shielding layer preventing distortion of the magnetic field at the internal conductor in conjunction with the second isolating layer, wherein a second pad is provided in the third conductive layer, the second pad being connected to the first end of the coil through the external peripheral portion of the first conductive layer.
The magnetic field probe and the magnetic field measuring system of the present invention are effective in preventing the distortion of the magnetic field at the lead wires between the coil and the pads within the probe, and provides adequate accuracy of a magnetic field measurement for the device under test in the vicinity of the probe. The magnetic field probe and the magnetic field measuring system of the present invention allow accurate measurement to be performed of a magnetic field signal within a radio frequency range, enable a three-dimensional measurement or vector measurement of a magnetic field to be performed, and allow accurate detection of a small magnetic field from the device under test to be performed. Also, it is possible to measure a distribution of a magnetic field from the device under test with high accuracy. By using the magnetic field probe and the magnetic field measuring system of the present invention, it is possible to obtain the results of the magnetic field measurement with high accuracy, and the results of the magnetic field measurement are useful to take preventive measures to reduce electromagnetic noise from electrical/electronic devices and printed circuit boards therein, so as to be in compliance with legal electromagnetic compatibility (EMC) controls. This makes it possible to reduce the period needed for development of new products.